Leptogium is a genus of lichen-forming fungi in the family Collemataceae.[1] It has about 110 species.[2] Species formerly classified under Leptogium have since been divided among the genera Leptogium, Pseudoleptogium, and Scytinium. Leptogium lichens are predominantly found on tree bark or soil, often among mosses, and sometimes on rocks in moist environments.[3]
Leptogium | |
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Leptogium phyllocarpum | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Lecanoromycetes |
Order: | Peltigerales |
Family: | Collemataceae |
Genus: | Leptogium (Ach.) Gray (1821) |
Type species | |
Leptogium lacerum (Sw.) Gray (1821)
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Leptogium is characterized by its foliose, gelatinous thallus, which varies in colour from blue-grey to olive-brown or blackish. The upper and lower cortex of these lichens consists of a single layer of roughly equal-sized cells. The medulla, on the other hand, is made up of loosely intertwined hyphae intermingled with chains of photobiont cells. The upper surface of the thallus can range from smooth to wrinkled or ridged, often exhibiting a glossy appearance, while the lower surface may be smooth, web-like, or hairy, sometimes featuring small clusters of white rhizines.[3]
Leptogium species often possess isidia and have Nostoc as their photobiont. The ascomata are apothecia, which can be sessile or shortly stalked and are predominantly laminal. The thalline margin may persist or become excluded, occasionally displaying a lobulate form. The true exciple is raised, cup-shaped, and mainly composed of periclinally arranged hyphae, with a colour that varies from colourless to reddish-brown. The disc of the lichen is either concave or flat.[3]
The epithecium is colourless to reddish-brown and does not react with solutions of either potassium hydroxide or ammonia. The hymenium is colourless and turns blue when exposed to iodine. The hypothecium is shallow and either colourless or pale yellowish. The hamathecium consists of numerous, conglutinate paraphyses with slightly swollen apices. The asci are club-shaped (clavate) and contain four to eight spores, with the wall and apical dome turning blue in response to potassium hydroxide and iodine. Ascospores are ellipsoidal, ovoid, or fusiform, sometimes featuring an apiculate end, and are septate and colourless. Lichen substances have not been detected by thin-layer chromatography in Leptogium species.[3]
As of April 2023[update], Species Fungorum (in the Catalogue of Life) accepts 84 species of Leptogium.[1]